The present invention is directed to a method for manufacturing preforms of glass which are subsequently drawn into optical fibers particularly for use in optical communications technology. The method includes generating glass particles from a vapor phase, collecting the glass particles and then subsequently applying the glass particles to a substrate to form a porous preform member which is subsequently utilized in forming optical fibers.
It has been previously known to form preforms of glass for subsequent drawing into optical fibers by generating glass particles from a vapor phase and applying these particles directly onto a substrate. These known methods of forming or depositing glass particles from a vapor phase are broken into four different species. These species principally are as follows:
(a) an OVD method wherein glass particles are directly deposited from a vapor phase onto a generated surface of an auxiliary rod;
(b) a MCVD method wherein the glass particles are directly deposited from a vapor phase onto the inside wall of a silica glass tube with the assistance of a burner;
(c) a PVCD method wherein the glass particles are directly deposited from a vapor phase onto the inside wall of a silica glass tube with the assistance of a plasma; and
(d) a VAD method wherein the glass particles are directly deposited from the vapor phase onto an end of a rod.
In all of the four methods, vaporous SiCl.sub.4, GeCl.sub.4, TiCl.sub.4, BCl.sub.3, BBr.sub.3, CCl.sub.2, F.sub.2 and POCl.sub.3 are converted into oxides in a hot or, respectively, plasma zone and these oxides are deposited in soot form onto the relatively cold surface of the substrate immediately thereafter. In a later step, the deposited soot is fused to clear glass or, respectively, is sintered clear. At the end, a rod-like preform is obtained from which the optical fiber can be subsequently drawn.
A common problem in all of the above-mentioned methods is that the production rate is still relatively low due to the low deposition rate. Moreover, a large part of the vapor-like and particle-like reaction gases are lost as exhaust gas and a large part of the product is also lost as waste.